The -E mode may be used in grep with the following characters preceded by '\'.

? Match is optional but may be matched at most once
"*" Must be matched zero or more times (without "")
+ Must be matched one or more times
{n} Must be matched n times
{n, } Must be matched n or more times
{n,m} Must be matched between n and m times

The above command tells grep to use extended mode, find "Cra", followed by any number of string, followed by space, followed by printable character, followed by "o", followed by three characters, and search this in another_text_file.